Fishing tool for wells



Oct. 15, 1940.

W. W. GIPSON ET JL FISHING TOOL FOR WELLS Filed Feb. lO, 1959 L27 A C.

30 uc. 3s

Fig. 3

WILLARD W. GIPSON' FRANCIS'N. Foss/m RICHARD H. LONG INVENTORS ATTORN EYS Psa-med ocr. 15, 1940 UNITED ISTATES PAT-'ENT OFFICE FISHING TOOL FOR. WELLS Willard W. Glplon, Taft, Francis N. Fossati, Bichmond, and Richard l1. Long, Oakland, Calif.

I'his invention relates to a device for recovering drilling tools and the like which have been lost at the bottom of a deep well bore, and particularly to a fishing tool which is adapted to be secured to the lost article by means of a flash weld performed by means of an electric current of high intensity owing for a very short period of time.

During the drilling of deep wells by the rotary method the drill bit is carried at the lower 4end of l" a long string of drill pipe through which mud fluid is circulated to carry cuttings to the surface of the ground, and also to plaster up the sides of the bore hole to prevent intrusion of water or gas. In very deep wells the extreme length of drill pipe 5v and the large forces which it is required to transmit often result in breakage of the drill pipe near lthe drill bit Where it is very difllcult to secure a ilshing tool of the conventional type.

'I'his invention comprehends broadly the pro- ;zu vision of a pair of electrodes which may be lowered through the mud yfluid vto make contact with the so-called -flsh or object to be recovered, together with means for imposing an electric current of considerable intensity but of lvery short 2J duration so that. the electrodes will make a flash weld and thereby be firmly secured to the sh.

It is contemplated that the electrodes and at least a part of the current control apparatus would be lowered in the bore hole by means of a steel :m cable, the latter serving to support the current carrying conductors to the electrodes and also serving to pull the fish out of the hole if and when it is caught.

It is an object of this Inventiontoprovide a iishing tool for removing metal parts which have become detached from the usual hoisting or drilling equipment in deep wells.

. Another object is to provide a fishing tool which will utilize a momentary electric current of v 40 high intensity to fuse or flash weld a pair of electrodes to a piece of metal which is lost in the bottom of a deep well.

'I'hese and other objects and advantagesof this invention will be further apparent from the following description and from the accompanying drawing, which forms a part of this specification and illustrates a preferred embodiment of this invention. f

In the drawing;v l Figure l is a connection diagram of one form of control apparatus for imposing a momentary flow of current on the electrodes.

Figure 2 is a diagram of an alternative form of apparatus for controlling the electric current impulseydelivered to the electrodes.

Figure 3 is a vertical sectional .view of a well bore showing an arrangement of the electrodes for performing the flash weld, together with a transformer and a cable for raising and lowering the entire equipment in the well. 5

In the drawing, and particularly referringto Figure 3, reference numeralr Ill designates a bore hole in the earth, a part of' which may be provided with a casing II. Below the lower end of casing I I and surrounded bythe usual mud fluid I2 l0 is the fish or object I3 which itis desired to recover from the well. In the example shown, this is illustrated as being a drill bit to which is attached a short section of drill pipe or drill collar.

At the lower'end of cable I4 is suspended a fluid 15 tight housing I5 in which is mounted a step-down electrical transformer I6 supplied with relatively high primary voltage, for example 44o-2300 volts A.. C., by means of a flexible insulated cable Il ,which enters housing I5 through a suitable stui'fzo lng box I 8.

s casing II to pre ent electrodes 2I in such a man- 80 ner-that they l contact ilsh I3.in two places. With these contacts established, thefprimary of the transformer I6 is momentarily energized'from a suitable electric power source, causing a very high current to flow through the secondary of '86 the* transformer and making a so-called ilash weld between electrodes 2l and fish I3. This will ordinarily be found adequate to permitfish Il to be drawnupwardly by cable I4 so that the usual drilling operations may be continued. 40

Referring no'w` to Figure 1 which illustrates one type of control means for impressing the momentary current on the' primary of transformer Il, reference numeral 25 designates a synchronous timer orwcommutator which isN driven by a syn- 45 chronous motor 25 from an alternating current power source 21. 'rimer 251s provided with/adr justable brushes 28 to be movableover 180'e1ectrical degrees so that contact may be made at any desired point on the positive half cycle ofthe 50 alternating current flow. Contact should be made by thetimer only once during each complete cycle.

"Iimer 25 is used to control the grid circuit of a three-element electronic tube 29 which in turn 55 controls the current now from the A. C. power source 21 through circuit 30 in which is connected the primary 3i of transformer I5. Circuit 30 includes the electric cable i1 of Figure 3.

Timer 25 is connected in series with a momentary contact switch 32 adapted to discharge condenser 33 through resistor 34. This discharge obviously takes place after the momentary contact switch is closed and at the instant that timer 25 is likewise closed. The voltage drop-across resistor 3l energizes the grid of tube 29 and permits current to flow from the alternating current power source 2T through transformer I6 for the remainder of that particular half cycle. Resistor 35, which is in series with condenser 33 and the direct current power source 3S, prevents the condenser from being charged to a-value which will give the grid of tube 29 a high enough potential to make it conducting during the succeeding positive half cycle.

.Figure 2 illustrates an alternative form of the control means just described and utilizes most of the same elements. Here again is a timer or commutator 25 driven from the alternating current power source 2l by a synchronous motor 26 and fitted with an adjustable brush rigging 28. Momentary contact switch 32 is adapted to discharge condenser 33 through the primary 31 of a small transformer 38. The secondary 39 of transformer 38 is connected to the igniter band 40 of a mercury tube 4|, impressing a high voltage between the band and the mercury 42 to cause current from the alternating current power source 21 to flow through circuit 38 which includes the primary 3| of transformer i6.

Obviously there are many other means by which the momentary current flow to the primary of transformer i6 could be controlled, these two merely serving as examples. The principal feature of novelty in this invention is considered to be the provision of a plurality of electrodes adapted to be lowered intp a Well bore to make contact With a metal object therein and to be supplied by a momentary high current flow which lmay be unidirectional, to complete a nach weld vchanges could be made and all such that fall within the scope of the appended claims are embraced thereby.

We claim:

1. In a nshing tool utilizing a low voltage transformer having a heavy alternating current flow of short duration through its secondary to make a flash weld with a metallic object; a timer for predetermining the length of time of iiow of the primary alternating current supply to said transformer comprising a normally non-conducting evacuated tube, a synchronous motor driven contactor connected to said tube, a source of direct current and a condenser adapted to be charged therefrom, and means for' discharging said condenser through said contactar and said tube to cause the latter to become conducting to said primary alternating current supply to said transformer during a predetermined portion of a, half cycle of said alternating current.

2. A fishing tool for deep wells comprising a transformer, a housing for said transformer adapted to be lowered into a well bore, means for transmitting a momentary high potential exciting current to the primary of said transformer from the top of said bore, a hinged yoke suspended from said transformer housing, a plurality of electrodes carried by said yoke, and ilexible conductors extending from said transformer secondary to said electrodes, said yoke acting to equalize the strain on said electrodes after they have been ash welded to a iish' in the well bore to raise the same to the surface. 

